An abandoned railroad tunnel is now filled with bioluminescent bugs.

An Australian lake whose pink hue defies scientific explanation.

This Gothic castle was inspired by Erik the Red's Viking residence at Brattahlid in Greenland.

A former medieval fortress, now home to Edinburgh Napier University, contains a rather risqué work of art.

The oldest surviving glass furnace cone in Western Europe.

An old saloon in the West filled with history, and according to some, a few dozen ghosts.

In England, a barn-turned-wedding venue dates back to the 13th century.

This castle played host to the largest great hall found in medieval Central Europe.

An abandoned facility that has become a place of ritualistic satanic worship, or so rumor has it.

The former home of the man whose radical ideas changed the nation.

In the ancient Woolley Woods, an art project promises access to new worlds.

The installation’s official name, “You Who Are Getting Obliterated in the Dancing Swarm of Fireflies,” says it all.

This oddly placed 15th-century church is one of only six bridge chapels left in England.

Rippling sand dunes frozen in the Arizona rock.

These unique weather vanes honor Scotland's most famous bard and decorate this walkway.

The skulls and bones of thousands of soldiers line the walls of this small Italian chapel.

One of the most well-preserved castles in Italy also contains a rare medieval example of a port fortification.

On the shores of Lake Garda, the ruins of a Roman villa that allegedly belonged to the poet Catullus.

A military museum, art park, mausoleum, and architectural oddity all on one fascist's estate.

A fiery crater has been burning in the Karakum Desert since 1971.

An abandoned tower once used to study the cosmos hides within a thicket of greenery.

Now abandoned, this stone church was part of the missionary efforts that initiated the Christianization of Zambia.

The dairy farm in upstate New York where nearly half a million people gathered for three days of peace and music in 1969.

Part of the medieval watchtower is displayed in an otherwise ordinary parking garage.